Stator blade construction



Patented June 10, 1952 TA QB BL D NSTR QITFQR Solomon 'Musik an t; Lodi, N.1f., sagas to our v H itiss-rwright Qq no fi a m afiq wi sler aware "1 Appli atipn Apr l 4, 1949 a 8535? l Months; (01. 23 3 invention relates to turbine power plants This structioii for some power plane a In a gas turbine powenplant; the combustion easel are directed against the turbine rotor blades by afpluralitybf*circuinferentially-spaced b1ades which, multi sfiag turbine, comprise the first stagof'th turbine'statorblades; In general the tempei'at' andisiparticularlirdirected to a stator blade "con-' ur'e' 'of' the combustion gases at the first stage stator blades is r'e'latively 16w adjacent theradially spaced en'ds'offeach blade and is relatively higlfadjacent a mid-portion of each blade, As a result there is a corresporiding ternperaturefof and along the stator object-of this invention comprises the stress in' ch stator blade is relatively low adjacent the lmideportion of each bladewhere the strength;of the blade materialis relatively lot because of the relatively high temperatureof this portion of the bladefduring "turbine" operation.

The s'tator'construction ofthce present inventionconiprises apair of co-axial rings, the one surrounding the 'other, with'a plurality of circumirentially sp ac'edblades extending therebetween: eachsaid-b'lade having a split two-part construction The'one part of each split stator blade is''supporte'd "as a cantilever and extends inwardly r dm the'outer or said rings and the other part of said blade is supported as a cantilever and extends outwardly from the inner of sa'id 'rings; the adjacent two" parts of each blade Figures3 and dare further enlargedsectional views takenalong 'linei 3+3 @1 4 respectively "Figure5 is a transverse sectional view of a m dified stator blade "construction Wttkil] along linei sor'ni'gureey Figure 6*"is" a'"sectional View taken along line a". a m; 4. L. J

ure'lis a'transverse sectional view taken line 7+! 8""aiidillustrating' a a"turb1nestatoif blade constructionsuch that further modificationrof :the stator blade construction; v'and i." s

Figure-H8 isa section 1 view taken along line 8-8Tof-Figure 7 i 'w: "1' 1-. 1 t f a;

'Referring first to Figure lot the drawing, a

' gas turbine power plant] O is schematically i1lustrated as comprising ancompressorr 12; an annular combustionchamber l4 and a multi-stage turbine l6. wrhe compressor lZ-ihasaforwardlyldirected air'inlet l81"anid supplies compressed air to the combustion chamber-J4: .Fuelrissupplied to the combustion chamber al 4-throrugh a-plurality. of fuel nozzles foracombustionitherein: and circumferentially s'paced guideivanes 22 directrthdcombustion gases against the :Jfirst stage rotor blades 2 4'of the-multi 'stage'turbine: :::-Thusthe guide vanes 22 comprise 3 then firstzistage stator; "blades r for"; the multi stage turbine I6..z"-Second .stage stator blades 26 guide and'direct thezcombustion gases against the second istage: rotor blades 238 .from which said gases discharge: irearwardly; through the exhaust duct 30 360 prlovidetthe'power plant with forwardpropulsivethrusti, Asiar asithe present inventioniis concerned the turbine 1 may have only one stage of rotor bladestor, itnmay have any desiredinumber of'wstages of saidr otor bladesivlwi .11 i e :The turbine I6 is drivably connected to the compressor l2: In additiomiin; thev-case 10f 'a power plant foran iaircrafti'or other. vehiclethe turbine Imay alsob'e drivably'iconnectedrtoisuit able vehicle propelling Ineans such'= as. the air craft propeller-"32! The structure :of. theppower plant It! so far dscribeduis conventionalr 1 1 The first stage stator blades.l2zaretransversely split intermediate their ends in'ithei region Where their operating temperature is the highest; This would generally be near the mid-portionbf the blades 22;" The detailsaof i :the stator structure are best seen in Figur'es 2 to4.4.= :Asuthere illustrated each'stator blade 22 is transversely" split at 34.1mm -two blade rparts 3 61 and l '38 Each stator blade pa'rtq36 has aniindividual shankflfl abutting the shanksfof the adj a'cent blade parts '36? "The shank :40 ot-leach blade part; 3:6 has a tdngue'd'z which is received within Landfill-111111311 groove iormedsina ring 44, "said ring! being secured to iorforming arcontinuation :of thejrouter annular wallt of the combustion; chamber M. In* addition-the shank 4.0 ctl'each statonrblade 36 has a'=flange': which is securedL betWeenthe fixed flanges "483 and -"50110f the powergplant. In thisefway the shank Mfofeach blade park-36 is rigidly secured tbiith'e fring whereby the blade parts'3 6- are each. supported "asaflcantilever from 3 the annular wall structure formed by the abutting shanks 40 of the blade parts 36.

As illustrated the blade parts 38 are formed integral with a ring or annular wall 52. Obviously, however, the blade parts 38 may be provided with individual shanks secured to the ring 52 in abutting relation, for example similar to the manner in which the shanks 40 of the blade parts 36 are secured to the ring 44. The ring 52 is secured to the fixed inner annular wall 54 of the combustion chamber 14. In this way each blade part 33 is supported as a cantilever from the ring 52 and extends radially outwardly therefrom.

The inner annular wall surface defined by the shanks 40 of the blade parts 36 is preferably in substantial alinement with a protective liner 56 for the outer annular wall of the gas turbine combustion chamber 14. Similarly the surface of the ring or annular wall 52, from which the blade parts 38 extend, is preferably in substantial alinement with a protective liner 58 for the inner annular wall of the combustion chamber M.

The two blade parts 36 and 38 of each stator blade 22 are disposed in longitudinal alinement. In order to maintain each pair of blade parts 36 and 38 in longitudinal alinement they are preferably provided with a tongue and groove fit or with some equivalent construction. As illustrated, each blade part 36 has a tongue-like projection 63 extending longitudinally from its end into a correspondingly shaped groove in its associated blade part 33. This tongue and groove fit also minimizes gas leakage between said parts.

With a tongue and groove fit between the blade parts 36 and 38, it is impossible to assemble said parts unless one of the parts 36 or 38 and the annular wall rigid with its shank ends has a multi-part construction. However it is not essential that each blade part 35 have its own individual shank 40 as illustrated. For example the annular wall defined by the shank end-s of the blade parts 36 could be divided into a plurality of sections each integral with a group of said blade parts.

The blade parts 33 and 33 are provided with a small amount of longitudinal clearance between their adjacent ends to permit free relative expansion of said parts, this clearance being indicated at the split 34 in Figures 2 and 3 and for purpose of illustration has been greatly magnified. With this construction, the blade parts 36 and 33 are free to expand longitudinally relative to each other as the turbine heats up without inducing stresses in the blades which would otherwise cause the blades to buckle as a result of differences in the expansion of the two ends of each blade 22.

The necessary longitudinal clearance between the two parts of each blade 22, such that there is no tendency for the blades to buckle as the turbine heats up, is small. The actual magnitude of this clearance will depend on the particular gas turbine installation. Thus this clearance need only be suificiently large to accommodate the difference in the radial expansion of the ring 44 and its blade parts 35 as compared to the radial expansion of the ring 52 and its blade parts 38 as the turbine heats up. Accordingly, the magnitude of this clearance will depend on the magnitude of the difference between the operating temperature of the ring 44, the blade shanks 4i] and their blade parts 33 and the operating temperature of the ring 52 and its blade parts 38.

In addition to said longitudinal clearance, and as illustrated in Figure 3, the tongue and groove fit between the parts 36 and 38 of each blade also has some lateral clearance. This lateral clearance is provided to permit each pair of blade parts to bend without binding under the combustion gas forces imposed thereon during turbine operation while their tongue and groove fit maintains the blade parts in substantial alinement. Like the longitudinal clearance between the blade parts 36 and 38 this lateral clearance is also greatly magnified in the drawing.

With the split blade construction described there is no tendency for the blades 22 to buckle as they expand when the turbine starts up. In addition because each blade part 36 and 38 is supported as a cantilever from its annular wall, the combustion gas forces against these blade parts impose practically no stress in the free or adjacent ends of the blade parts 36 and 33. As a result, the stress in each blade 22 is a minimum at its intermediate portion at the split 34 where its temperature is the highest during turbinev operation and said stress is a maximum adjacent the shank ends of the blade parts 35 and 38 where the blade temperature is relatively low. Accordingly, during turbine operation, the stress in each blade 22 is a minimum where the strength of the blade material is weakest and said stress is a maximum where the strength of the blade material is the strongest.

If each blade 22 had a one-piece construction and were entirely supported from only one or the other of the rings 44 or 52 the combustion gas forces against the blades would cause appreciable stresses in the high temperature intermediate portion of each blade. On the other hand if the lades 22 had a one-piece construction and were fixedly secured to both rings 44 and 52 then, if the turbine were started up, the blades Would tend to buckle because of unequal radial expansion of the two ends of the blades.

In lieu of the tongue and groove fit between each pair of blade parts 36 and 38, said parts may simply be formed so that they substantially abut. In addition, where a tongue and groove fit is provided between each pair of blade parts 36 and 38 said fit need not have the construction illustrated in Figures 2 to 4. For example in Figures 5 to 6 each blade part 35 has a tongue 62 which instead of having a tapered cross section and instead of following the curvature of its blade 22, has a rectangular cross section and is flat. Each tongue 62 is secured within a correspondingly shaped groove in its adjacent blade part 38. A further modification is illustrated in Figures 7 to 8 in which each tongue 60 or 62 has been replaced by one or more dowel-like projections 64 which extend longitudinally from their blade part 36 into correspondingly shaped recesses in the adjacent blade part 33.

The invention has been described in connection with and is primarily useful in connection with the first stage turbine stator blades because of the high temperature of the combustion gases at these blades. Obviously, however, the invention is not limited to these particular stator blades. For example, it may be desirable to construct the blades of the last stator stage of the axial flow compressor l2 in a similar manner.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications.

I claim is my invention:

1. A stator blade structure for a turbine, compressor or the like; said structure comprising means providing a first annular wall; means providing a second annular wall co-axial with and surrounding said first wall; and a plurality of circumferentially spaced blades bridging the annular space between said walls, each of said blades having a split two-part construction, the one part of each blade being supported as a cantilever and extending inwardly from the outer of said walls, the other part of each blade being supported as a cantilever and extending out- Wardly from the inner of said walls.

2. A stator blade structure as recited in claim 1 in which the adjacent ends of the two parts of each blade are provided with a tongue and groove fit.

3. A stator blade structure as recited in claim 1 in which the one part of each blade has a tongue-like projection which extends longitudinally therefrom into a groove in the adjacent end of the other part of said blade.

4. A stator structure as recited in claim 1 in which the adjacent ends of the two parts of each blade have longitudinally overlapping portions to maintain said parts in longitudinal alinement and permit relative longitudinal movement of said two parts.

5. A stator blade structure for a turbine, compressor or the like; said structure comprising means providing a first annular wall; means pro viding a second annular wall, said walls being co-axial with the one surrounding the other; and a plurality of circumferentially spaced blades bridging the annular space between said walls, each of said blades having a split two-part construction with the one part of each blade being supported as a cantilever from said first wall and extending from said first wall toward said second wall and with the other part of each blade being supported as a cantilever from said second wall and extending from said second wall toward said first wall, the adjacent ends of the two parts of each blade having longitudinally overlapping portions to maintain said parts in longitudinal alinement and to permit relative longitudinal movement of said two parts, and one of said walls and its blade parts having a multi-part construction to permit assembly of the two parts of each blade in longitiudinally overlapping relation.

6. A stator blade structure for a turbine, compressor, or the like; said structure comprising means providing a first annular wall of relatively small diameter; means providing a second annular wall of relatively large diameter coaxially disposed about said first wall; a first set of circumferentially spaced stator blade elements, each of said blade elements being supported as a cantilever from said first wall and extending outwardly therefrom part way toward said second wall; a second set of circumferentially spaced stator blade elements, each 01 the blade elements of said second set being supported as a cantilever from said second Wall and extending inwardly therefrom part way toward said first wall, each blade element of one set cooperating with a blade element of the second set to form a complete blade bridging the space between said Walls.

7. A stator blade structure for a turbine, compressor, or the like; said structure comprising means providing a first annular wall of relatively small diameter; means providing a second annular wall of relatively large diameter coaxially disposed about said first wall; a first plurality of circumferentially spaced stator blade elements, each of said blade elements being supported as a cantilever from said first wall and extending outwardly therefrom approximately halfway toward said second wall; a second plurality of circumferentially spaced stator blade elements, each of the blade elements of said second plurality being supported as a cantilever from said second wall and extending inwardly therefrom approximately halfway toward said first wall each blade element of said first plurality being substantially alined with a blade element of said second plurality to form a complete blade.

8. A gas turbine stator structure for directing the turbine motive fluid against the turbine rotor blades; said stator structure comprising means providing a first annular wall of relatively small diameter; means providing a second annular wall of relatively large diameter concentrically disposed about said first wall; and a plurality of circumferentially spaced blades extending between said walls, each of said blades having a split two-part construction, the one part of each blade being supported as a cantilever and extending outwardly from the first of said walls and the other part of each blade being supported as a cantilever and extending inwardly from the second of said walls.

9. The stator structure recited in claim 8 in which the adjacent ends of the two parts of each blade have longitudinally overlapping portions to maintain said parts in longitudinally alinement and permit relative longitudinal movement of said two parts.

10. A gas turbine stator the turbine motive fluid against the turbine rotor blades; said structure comprising means providing a first annular wall; means providing a second annular wall of greater diameter than and concentrically disposed about said first annular wall; a plurality of circumferentially spaced blades extending between said walls, each of said blades having a split two-part construction, the one part of each blade being supported as a cantilever from said first wall and extending outwardly therefrom toward said second wall and the other part of each blade being supported as a cantilever from said second wall and extending inwardly therefrom toward said first wall; and a tongue-like projection extending longitudinally from one part of each blade into a groove in the adjacent end of the other part of said blade.

structure for directing SOLOMON MUSIKANT.

REFERENCES CITED UNITED STATES PATENTS Name Date Judson Nov. 22, 1949 Number 

